Project Manager: Dr. Dana Georgeta Popescu - Cercetător ştiinţific gradul II

Dr. CS I Marius-Adrian Husanu
Dr. CS II Rasoga Oana
Dr. CS III Bogdan Ostahie
Dr. CS III Arpad Mihai Rostas
Drd. Marian Cosmin Istrate

The objectives of the RaBit project are:
O1. To prepare Rashba spin-orbit coupled ferromagnet - FM/Ge(111) (FM=Mn, Fe, Ni) interfaces by molecular beam epitaxy (MBE)
O2. To prepare multiferroic Rashba coupled interfaces FM/GeTe(111) FM=Mn,Ni,Fe
O3. Deduce the electronic structure of FM/Ge(111) and FM/Ge(Te(111), FM=Mn,Fe,Ni
O4. Prove the combined FE/FM functionality, showing that applied electric field couples with the magnetism with the spin texture (hence the flow direction) of the substrate controllable by the FE direction, while spin to charge conversion via inverse Edelstein effect results in modified ferroelectricity due to modified compensation mechanisms of the FE state.

Summary of Stage I/2022:
The objective of the first stage of the "Integrated Rashba-type platform for data storage and bit manipulation" project, 100% completed, consists in the preparation and characterization of FM/Ge(111) type interfaces (FM=Mn, Fe, Ni). In the first phase, we experimentally developed the 3 interfaces by the molecular beam epitaxy of metals (Mn, Ni, Fe) on the Ge(111) substrate, followed by the structural characterization of FM/Ge(111) by LEED to confirm epitaxial growth. Photoelectron spectroscopy on FM/Ge(111) samples allowed us access the electronic structure of the interfaces, and ab-initio calculations by the density functional theory (DFT) method facilitated a more thorough description of the studied interfaces. Relaxation of iron, manganese and nickel on the Ge substrate using relativistic pseudopotentials tells us the local distortions and reconstructions at the interface and establishes the contribution to the electronic structure of each element. The relaxed structure obtained by DFT is the input for the tight-binding calculations, which gave us the spectral function and the theoretical description of the spins and charge currents for the Rashba-type coupled interfaces. The first stage of the TE50/2022 project was completed with the publication of an article, an article under review, participation in 3 international conferences and the registration of a patent at OSIM.

Delivered results:

• The development of three new nanomaterials used for the further study of Rashba-type spin-orbit splitting;
• 6 scientific communications held at international conferences;
• 2 book chapters;
• 1 article published in journals indexed in Web of Science®, and 1 article sent for publication;
• 1 patent sent to OSIM

The scientific report will not be presented on the project website, the results are in the process of being published.

2022: Scientific report no. 1 in *.pdf format is available and can be accessed on request at UEFISCDI.

Summary of Stage II/2023:
The objective of the second stage of the "Integrated Rashba-type platform for data storage and bit manipulation" project, realized in 100% proportion, consists in the manufacture and characterization of FM/GeTe type multiferroic interfaces (FM=Mn, Fe, Ni). In the first phase, we experimentally realized the 3 interfaces consisting of the molecular beam epitaxy deposition of metals (Mn, Ni, Fe) on the GeTe/Ge(111) substrate, followed by the structural characterization of FM/GeTe(111) by low energy electron diffraction. Photoelectron spectroscopy on FM/Ge(111) samples allowed us access to the electronic structure of the interface (from where we could calculate the stoichiometry and describe the mechanism of band bending at the interface). The ab-initio calculations by the functional theory method of density (DFT) and tight binding facilitated a more thorough description of the studied interfaces. Relaxation of iron, manganese and nickel on the GeTe substrate using relativistic pseudopotentials shows us the local distortions and reconstructions at the interface and establishes the contribution to the electronic structure of each element. The relaxed structure obtained by DFT was the input for the tight-binding calculations, which gave us the spectral function and the theoretical description of the spins and charge currents for the Rashba-type coupled interfaces. X-ray diffraction measurements allowed us to find out details about the lattice constants and growth modes of the materials. Transmission electron microscopy measurements revealed details about the positioning of the atoms. In order to find out information about the spin-orbit functionality, ferromagnetic resonance measurements were performed in the radio frequency X band, and in order to reproduce the intrinsic electronic structure of the studied surfaces, angular resolved photoemission and spin measurements were performed at the synchrotron facilities, where measurements of X-ray absorption were also conducted. The second stage of the TE50/2022 project was completed with the publication of an article, participation in 2 international conferences and 3 participation at European Exhibition of Creativity and Innovation.

Delivered results:

• Development of three new nanomaterials: (Fe,Mn,Ni)/GeTe/Ge(111);
• 7 scientific communications held at international conferences;
• 2 articles published in journals indexed in Web of Science®, and 1 article sent for publication;
• 1 patent sent to OSIM.

The scientific report will not be presented on the project website, as the results are still being published.

2023: Scientific report no. 2 in *.pdf format is available and can be accessed upon request at UEFISCDI.

Summary of Stage III/2024:
The objective of the third stage of the "Integrated Rashba-type platform for data storage and bit manipulation" project, achieved in 100% proportion, was to demonstrate the coupling between ferroelectric and ferromagnetic materials. In the first phase, we performed ferromagnetic resonance measurements in the radiofrequency X band to find out information about the spin-orbit functionality. Then we validated through electrical and magnetic measurements the coupled functionality between ferroelectric and ferromagnetic materials using the PPMS (Quantum Design) system from the National Institute of Materials Physics, confirming the multiferroic character of the structures made in the previous stages. Ab-initio calculations by the method of density functional theory (DFT) and tight binding allowed a more thorough description of the studied interfaces. The third stage of the TE50/2022 project was completed with the submission of two articles for publication, the participation in 1 international conference and the publication of 2 book chapters and a national patent.

Delivered results:

• Demonstration of the coupling between ferroelectric and ferromagnetic materials;
• 1 scientific communication held at an international conference;
• 2 articles sent for publication;
• 2 book chapters;
• 1 patent sent to OSIM.

The scientific report will not be presented on the project website, as the results are still being published.

2024: Scientific report no. 3 in *.pdf format is available and can be accessed upon request at UEFISCDI.

Outcome/results:

Published/in-press articles:
1. M.A. Husanu, D.G. Popescu, F. Bisti, L.M. Hrib, L.D. Filip, I. Pasuk, R. Negrea, M.C. Istrate, L. Lev, T. Schmitt, L. Pintilie, A. Mishchenko, C.M. Teodorescu, V.N. Strocov Ferroelectricity modulates polaronic coupling at multiferroic interfaces, Communications Physics 5, 209 (2022).
2. D.G. Popescu, M.A. Husanu, P. C. Constantinou, L.D. Filip, L. Trupina, C.I. Bucur, I. Pasuk, C. Chirila, L.M. Hrib, V. Stancu, L. Pintilie, T. Schmitt, C. M. Teodorescu, V.N. Strocov, Experimental band structure of Pb(Zr,Ti)O3: Mechanism of ferroelectric stabilization, Advance Science 10, 2205476 (2023).
3. A.I. Borhan, A.I. Ghemes, M.A. Husanu, D.G. Popescu, C.N. Borca, T. Huthwelker, I. Radu, A.C. Dirtu, D. Dirtu, G. Bulai, N. Lupu, M.N. Palamaru, A.R. Iordan, D. Gherca, Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics, Appl. Surf. Sci. 622, 156987 (2023).
4. Radu Ioana, Borhan Adrian Iulian, Gherca Daniel, Popescu Dana Georgeta, Borca Camelia Nicoleta, Huthwelker Thomas, Bulai Georgiana, Husanu Marius-Adrian, Pui Aurel, Al-doped SrTiO3's secrets in structure, morphology, and electronic contributions for enhanced photocatalytic O2 evolution from water splitting, trimis spre publicare Chemistry of Materials (2023)
5. In-operando XPS investigation on enhanced charge transfer and lattice oxygen oxidation in aliovalent doped and δ-FeOOH surface decorated of Al3%:SrTiO3 perovskite photocatalyst, trimis spre publicare Journal of Materials Chemistry A (2023).
6. Alexandru-Cristi Iancu, Nicoleta G. Apostol, Adela Nicolaev, Laura E. Abramiuc, Cristina F. Chirilă, Dana G. Popescu, Cristian M. Teodorescu, Swinging molecular adsorption of carbon monoxide on ferroelectric BaTiO3(001), Journal of Materials Chemistry A (2024)

Book chapters:
1. Compensation and screening of ferroelectricity in perovskite oxides, D.G. Popescu, M. Husanu, Perovskites: Ceramics, Editors: J.L. Clabel H. and V.A.G. Rivera, Elsevier 2022, ISBN: 9780323905862
2. Polaronic effects in perovskite oxides, M. Husanu, D.G. Popescu, Perovskites: Ceramics, Editors: J.L. Clabel H. and V.A.G. Rivera, Elsevier,2022, ISBN: 9780323905862
3. C. Chirila, A.G. Boni, L.D. Filip, M. Botea, D. Popescu, V. Stancu, L. Trupina, L. Hrib, R. Negrea, I. Pintilie, L. Pintilie, Epitaxial ferroelectric thin films -Potential for new applications, book Pulsed Laser Processing Materials, IntechOpen 2024, ISBN: 978-0-85466-611-9
4. D.G. Popescu, Fundamental and functional perspective of ferroelectric BaTiO3 from an electron spectroscopy perspective, book Nanocomposites - Properties, Preparations and Applications, IntechOpen 2024, ISBN: 978-0-85014-082-8

Patent Requests:
1. D.G. Popescu, M.A. Husanu, 2D Photonic Crystal in Ge Matrix, A/00668 - 2022
2. M.A. Husanu, D.G. Popescu, C. Chirila, C. Besleaga-Stan, Tranzistor cu efect de câmp din oxizi, operat printr-un dublu strat electronic dublu și metodă de realizare, A 2023 00775
3. D.G. Popescu, M.A. Husanu, Tranzistor din GeTe cu efect de câmp și poarta divizată depus pe semiconductori (Si,Ge si SiGe) și metodă de realizare, A 2024 00240

International conferences:
1. D.G. Popescu, M.A. Husanu, Experimental band structure of ferroelectric Pb(Zr,Ti)O3 and what can we learn from it, EMRS Spring, Strasbourg, France, May 29 – July 2 (2023) – oral presentation;
2. M.A. Husanu, D.G. Popescu, L.D. Filip, L.M. Hrib, L. Pintilie, C.M. Teodorescu, V.N. Strocov, Impact of ferroelectricity on the electron-phonon coupling at oxide interfaces, EMRS Spring, Strasbourg, France, May 29 – July 2 (2023) – oral presentation;
3. D.G. Popescu, L.D. Filip, C. Chirila, L. Hrib, M.A. Husanu, Bulk band splitting due to spin-orbit interaction in ferroelectric oxides, Topological Matter, Athens, Greece, March 28 - 31 (2023)
4. M.A. Husanu, A.C. Iancu, R.M. Costescu, D.G. Popescu, Bulk and surface – related nature of Ge(111) spin-orbit split bands, Topological Matter, Athens, Greece, March 28 - 31 (2023)
5. D.G. Popescu, L. Borcan, A. Iancu, A. Rostas, C. Ruxandra, V. Strocov, M.A. Husanu, Rashba coupling in metallic states at the Ni-doped Ge interface, The 7th International Colloquium „Physics of Materials”, Bucharest, Romania, November 10 - 11 (2022)
6. M.A. Husanu, A. Iancu, D. G. Popescu, C. Chirila, C. M. Teodorescu, Orbital character of two dimensional electron gas at an oxide interface, The 7th International Colloquium „Physics of Materials”, Bucharest, Romania, November 10 - 11 (2022)
7. D.G. Popescu, M.A. Husanu, R. Costescu, L. Borcan, Rashba coupling in metallic states at the metal/semiconductor interface, 20th International Balkan Workshop on Applied Physics and Materials Science, Constanta, Romania, July 12-15 (2022)
8. M.A. Husanu, V. N. Strocov, D.G. Popescu, Modified occupancy of the orbitals at the conducting interface LaAlO3/SrTiO3, 20th International Balkan Workshop on Applied Physics and Materials Science, Constanta, Romania, July 12-15 (2022)
9. D.G. Popescu, M.A. Husanu, C. Chirila, L. Pintilie, C.M. Teodorescu, Impact on Ferroelectricity and Band Alignment of Gradually Grown metal on BaTiO3, International Conference on Strongly Correlated Electron Systems, Amsterdam, The Netherlands, July 24-29 (2022)
10. D.G. Popescu, L.D. Filip, C.I. Bucur, C. Chirila, L. Pintilie, T. Schmitt, C.M. Teodorescu, M.A. Husanu, V.N. Strocov, Stabilization mechanisms of opposed ferroelectric states, International Conference on Strongly Correlated Electron Systems, Amsterdam, The Netherlands, July 24-29 (2022)
11. Speaker la "Empowering Women - Challenges and Opportunities" March 2023
12. D.G. Popescu, European XFEL Users’ Meeting - Workshop: Grazing-incidence X-ray experiments using FELs; DESY Photon Science Users' Meeting, In situ energy-dispersive XRD and imaging on materials; High Energy X-ray Diffraction for Physics and Chemistry, Hamburg, Germany, January 22-24 (2024)
13. M.A. Husanu, D.G. Popescu, P.C. Constantinou, L.D. Filip, L. Trupina, C.I. Bucur, I. Pasuk, C. Chirila, L.M. Hrib, V. Stancu, L. Pintilie, R. Negrea, M.C. Istrate, L. Lev, T. Schmitt, C.M. Teodorescu, V.N. Strocov, Intrinsic electronic structure of oxide surfaces and interfaces from angle resolved photoelectron spectroscopy, 10th International Conference on Advanced Materials, July 15-18 (2024) – prezentare orala;
14. D.G. Popescu, M.A. Husanu, I. Radu, A.I. Borhan, D. Ghercă, C.N. Borca, T. Huthwelker, G. Bulai, G. Stoian, A. Pui, Al-doped SrTiO3 photocatalyst with increased performance, 10th International Conference on Advanced Materials, July 15-18 (2024);
15. L.E. Borcan, A.C. Iancu, D.G. Popescu, N.G. Apostol, A. Nicolaev, R.M. Costescu, M.A. Husanu, G.A. Lungu, C.F. Chirilă, C.A. Tache, C.M. Teodorescu, Surface Magnerism of Pt(001) and SrTiO3(001) investigated by spin-resolved photoelectron spectroscopy, TIM24 International Physics Conference, May 30 – July 1 (2024) – prezentare orala;

Dr. Ing. Dana Popescu

Scientific Researcher II
National Institute of Materials Physics
Atomistilor Str. 405A
077125 Magurele-Ilfov
Romania
Telephone: +40-(0)21-3690185, +40-(0)21-2418100
Fax: +40-(0)21-3690177